Many measurement and control applications are solved by using a central controller, in conjunction with remotely located sensors or actuators. In the past, these transducers were connected to the central controller, via a point-to-point link, either an analog, e.g. a 4-20 ma loop, or a digital link such as a RS-232. Recently, a number of "fieldbusses" have emerged that allow these devices to share a packet-based bus or network for communication to the central controller. In principle, these networks also allow peer-to-peer communication, where one smart device communicates directly to another. These networks establish the communication patterns over this shared media using addressing schemes, a process known as "binding".
The binding process modifies configuration tables in one or more computer components (system nodes), such that information packets placed on the network by an application executing on one node (node application) are correctly received by other applications. Most systems use a tag-based architecture for binding, where each network visible entity generated by these node applications is given a unique name. The binding occurs by properly associating the tags of sending and receiving entities and mapping these associations onto the addressing scheme of the underlying network protocol. Most network vendors have installation tools used to accomplish this binding. The installation tool methodology depends upon whether the binding occurs at design time, at commission time, or dynamically when components are replaced or the system is modified.
Except for systems where the bindings occur at design time, these tools typically access the network from a separate computer and individually access the distributed nodes for identification purposes. At a minimum, the factory built-in unique address (UUID) of each node is determined so that the tools can communicate with the device to modify the address tables. At the field level, the tools are implemented in lap-top computers or special purpose handheld devices, often in concert with a simple physical interface, e.g. a button on the remote component. If the node is akin to a computer, then the tools are often part of a separate user interface resident on the processor.
In all cases, the binding process requires specific design information about the global application which determines the communication among the applications executing on the distributed nodes. Typically for initial installation, this involves manual entry and often requires that this information and the resulting bindings be maintained in a form accessible to the tools in the event that system modifications are necessary. These tools usually require users who are computer literate and possess a detailed understanding of the application.
For distributed measurement and control systems, many application specific details for binding concern the identification of specific transducers, i.e. sensors and actuators, with some aspect of the physical world. To illustrate, the system must be aware which pressure sensor is measuring the pressure of boiler-1, as opposed to another point in the system. Since the pressure of boiler-1 is of interest at various points in the system, the information must be consistent system wide. Large systems are often hierarchical. As a result, the binding process is repeated at various levels of the system with different naming schemes. Again, the installers must properly match the names across these boundaries so that at all points of interest the pressure of boiler-1 is uniquely identified. In addition, distributed systems must establish communication patterns among collections of node applications (virtual node applications) that in concert behave as a larger application. Like a single application, collections can form hierarchies or other patterns that need a binding process.